Mechanical channel filters meeting CCITT specification

The paper elucidates the important role played by mechanical filters in modern carrier frequency communications systems. Mechanical filters offer the benefits of small volume, high Q, high stability, and low manufacturing cost. The design of mechanical filters is based upon the close analogy between electrical quantities and mechanical quantities. It is shown how the filter design takes account of certain peculiarities resulting from both fabrication requirements and circuitry of the modems. The detailed description of the fabrication process includes the impact of the material properties and of the available manufacturing technologies. While the first generation of mechanical channel filters had only 20 percent of its LC predecessor´s volume, the second generation achieves further miniaturization of another 60 percent. The paper concludes with an estimate of future trends toward miniaturization as well as toward improved transfer characteristics.